# CVE-2026-125269: FFmpeg double free in H.264 SEI message handling

Source: https://junglewise.ai/threats/cve-2026-125269-ffmpeg-through-9-0-2-contains-a-double-free-vulnerability-in  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-09. Updated: 2026-11-09  
License: CC BY 4.0 with a link back

CVE-2026-125269 · Severity: high · CVSS 7 · Published 2026-11-09

FFmpeg is a multimedia framework used to process video and audio files. A vulnerability in its H.264 video decoder allows an attacker to supply a crafted video file that triggers a double-free memory error, potentially enabling code execution or application crash. This affects any system using FFmpeg to decode untrusted video content.

Technologies: [Ffmpeg](https://junglewise.ai/threats/technologies/ffmpeg). Vendors: [Ffmpeg](https://junglewise.ai/threats/vendors/ffmpeg).

## Quick answers

**Is CVE-2026-125269 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-125269 being exploited in the wild.

**How severe is CVE-2026-125269?** High severity, with a CVSS score of 7, published 9 November 2026.

**Which products and versions are affected?** Ffmpeg through 9.0.2.

**Is there a fix for CVE-2026-125269?** Yes: fixed in FFmpeg 9.1. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-125269 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-125269?** Check whether you run Ffmpeg at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in FFmpeg 9.1

## Technical details

A double-free vulnerability exists in libavcodec/cbs_sei.c where cbs_sei_delete_message() fails to clear the extension_data reference that ff_cbs_sei_add_message() later reuses. An attacker can craft an H.264 bitstream containing a display orientation SEI message with payload extension data, processed by h264_metadata with display_orientation=insert, to corrupt the heap and potentially achieve arbitrary code execution.

## Affected products

- FFmpeg FFmpeg through 9.0.2

## Timeline

- 2026-11-09: disclosed
- 2026-11-05: patched: Fix merged via PR #25020

## References

- [https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/25020](https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/25020)
- [https://github.com/FFmpeg/FFmpeg](https://github.com/FFmpeg/FFmpeg)

## Related threats

- [FFmpeg heap out-of-bounds read in v4l2_buffers](https://junglewise.ai/threats/cve-2026-125270-ffmpeg-through-9-0-2-contains-a-heap-out-of-bounds-read)
- [FFmpeg heap out-of-bounds write in APAC decoder](https://junglewise.ai/threats/cve-2026-125267-ffmpeg-before-8-1-3-and-9-x-before-9-0-2-contains-a-heap-out-of)
- [FFmpeg use-after-free in NVIDIA codec decoding](https://junglewise.ai/threats/cve-2026-125265-ffmpeg-through-9-0-2-contains-a-use-after-free-vulnerability-in)
- [FFmpeg JPEG XL parser uncontrolled resource consumption](https://junglewise.ai/threats/cve-2026-125264-ffmpeg-through-9-0-2-contains-an-uncontrolled-resource)
- [FFmpeg LCEVC dimension validation bypass memory exhaustion](https://junglewise.ai/threats/cve-2026-125263-ffmpeg-9-0-through-9-0-2-built-with-liblcevc-dec-fails-to)